WO1981003710A1 - Ac biasing of a dc squid - Google Patents

Ac biasing of a dc squid Download PDF

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Publication number
WO1981003710A1
WO1981003710A1 PCT/US1981/000791 US8100791W WO8103710A1 WO 1981003710 A1 WO1981003710 A1 WO 1981003710A1 US 8100791 W US8100791 W US 8100791W WO 8103710 A1 WO8103710 A1 WO 8103710A1
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WO
WIPO (PCT)
Prior art keywords
junctions
frequency
squid
bias
bias current
Prior art date
Application number
PCT/US1981/000791
Other languages
French (fr)
Inventor
M Simmonds
R Giffard
Original Assignee
She Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by She Corp filed Critical She Corp
Priority to DE8181901786T priority Critical patent/DE3176411D1/en
Publication of WO1981003710A1 publication Critical patent/WO1981003710A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/035—Measuring direction or magnitude of magnetic fields or magnetic flux using superconductive devices
    • G01R33/0354—SQUIDS
    • G01R33/0356—SQUIDS with flux feedback
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
    • Y10S505/842—Measuring and testing
    • Y10S505/843—Electrical
    • Y10S505/845—Magnetometer
    • Y10S505/846—Magnetometer using superconductive quantum interference device, i.e. squid

Definitions

  • This invention relates to measuring circuits using superconducting quantum interference devices (SQUID) , and more particularly, to a biasing arrangement for reducing low frequency noise.
  • SQUID superconducting quantum interference devices
  • Quantum interference effects in superconducting rings containing one or two Josephson junctions are well known. Devices exhibiting these effects, known as superconducting quantum interference devices or SQUIDS, have been used, for example, in the measurement of magnetic fields and voltages. Both dc SQUIDS using two Josephson junctions connected in a superconducting ring and RF SQUIDS incorporating a single junction in a superconducting ring have been used for making such measurements. Such dc SQUIDS have recently been constructed using thin film Josephson junctions having oxide or semiconductor barriers. Such dc SQUIDS have been shown to have advantages in regard to magnetic energy sensitivity compared to the RF SQUID.
  • tunnel junction dc SQUIDS The construction and operation of tunnel junction dc SQUIDS is described in detail in the article "Tunnel Junction dc SQUID: Fabrication, Operation, and Performance” by Clarke, Goubau, and Ketchen, Journal of Low Temperature Physics, Vol. 25, Nos. 1/2, 1976, pp. 99-143.
  • Recent efforts at obtaining improved energy sensitivity have involved the use of very small area junctions which, because of their relatively low capacitance, make possible higher resistance SQUIDS.
  • Such small area junctions (approximately 1 ⁇ diameter) are able to operate in the earth's ambient field, thus avoiding the problem of providing a low field environment.
  • the present invention is directed to a biasing arrangement for a dc SQUID which removes substantially all l/f (low frequency) noise from the output signal of the SQUID.
  • the circuit is able to take full advantage of the high frequency sensitivity of very small area thin film junctions. This is achieved, in brief, by providing a biasing circuit for a dc SQUID having a pair of thin film Josephson junctions connected in a superconducting ring wherein a bias current is caused to flow through the two junctions in parallel alternately in one direction and then in the opposite direction by a squarewave oscillator.
  • This squarewave bias has no dc component.
  • the operating characteristics of Josephson junctions are symmetric so the SQUIDS operate normally except during the relatively short transition time of the polarity reversal.
  • the effect is to heterodyne the signal up to frequency bands centered around the squarewave frequency and its harmonics, which frequency is chosen to be well above any signal frequencies of interest, as well as the frequency at which the 1/f noise is significant.
  • FIG. 1 is a schematic showing of a dc SQUID
  • FIGS. 2 and 3 are graphical representations useful in explaining the operation of the present invention.
  • FIG. 4 is a schematic block diagram of the preferred embodiment of the present invention.
  • FIG. 5 is a timing diagram showing waveforms at various points in the circuit of FIG. 4.
  • the basic dc SQUID includes a low inductance superconducting loop 10 interrupted by two matched Josephson junctions 12 and 14.
  • a dc biasing current I B is passed through the two junctions in parallel, the voltage V J varies as a function of the flux ⁇ A threading the ring.
  • the voltage in fact, is an oscillatory function of the flux in which one period corresponds to one flux quantum ⁇ O .
  • FIG. 2 is graphical plot showing the change in the voltage V J as a function of the biasing current I B .
  • the voltage varies between two limits, indicated at A and C.
  • the present invention utilizes a squarewave signal for generating the bias current I B so that the operating point is switched each half cycle of the squarewave between the levels +I B and -I B .
  • the frequency F of the squarewave is selected above the normal range of signals being measured and preferably is in the order of 0.5 megahertz.
  • the preent invention superimposes the bias switching on the modulation and demodulation scheme used in the feedback loop.
  • the preferred embodiment for implementing the invention is shown in detail in FIG. 4, which operates to both switch the bias and apply modulation to the SQUID and then demodulate the resulting mixture to recover the original input signal spectrum.
  • the waveforms shown in FIG. 5 are useful in analyzing the operation of the circuit in the time domain.
  • the SQUID with its Josephson tunnel junctions 12 and 14 connected in a superconductive ring 10, is connected as one leg of a bridge circuit.
  • a second adjacent leg of the bridge circuit is a resistor 16.
  • the other two legs of the bridge circuit include respectively a resistor 18, capacitor 20 and bias modulator 22 forming one leg, and a resistor 24, capacitor 26 and balance modulator 28 forming the other leg.
  • a squarewave voltage is applied across one diagonal of the bridge by a squarewave oscillator 30 running at a frequency 2F and binary counter 32 which generates output squarewaves at frequencies F and F/4.
  • the bias modulator 22 in combination with the resistor 18 and capacitor 20 controls the amplitude of the switched bias current driven in parallel through the Josephson junctions 12 and 14.
  • the bias modulator 22 is controlled by a feedback circuit, described below. It automatically adjusts the amplitude of the switched current applied to the junctions, biasing them alternately between the average voltages +V O and -V O , as shown in FIG. 2.
  • the actual information signal is in the small amplitude variations around +V O and -V O which are induced by flux changes in the loop 10, such as by an input signal applied to an input coil 34 associated with the SQUID. These voltage variations are detected by an output transformer 36 whose primary winding 38 is connected through a blocking capacitor 40 across the other diagonal of the bridge circuit.
  • the secondary winding 42 of the transformer is connected to an RF amplifier 44.
  • the carrier voltage appears as a common mode signal at the transformer input and is rejected while any variations of the junction voltage from the nominal values -V O appear differentially at the transformer and are amplified by the RF amplifier 44.
  • the actual value of V O is set by adjusting the amplitude control signal V B on the input of the balance modulator 28.
  • the adjustable bias voltage source may be a potentiometer or similar device for controlling the output voltage of the balance modulator 28.
  • bias demodulator 48 Any carrier signal at frequency F which has been amplified by the RF amplifier 44 is demodulated by a bias demodulator 48.
  • the output of the bias demodulator 48 is an error signal which is integrated by an integrator circuit 50 and applied to the bias modulator 22 to control the output voltage level of the bias modulator. It should be noted that it would be possible to arrange this circuit to manually set the junction bias current and have the bias voltage automatically adjusted. However, because the voltage is less prone to variation than the operating current, adjustment of the voltage as the independent variable is preferred.
  • the time constant of the integrator 50 is made long enough so that negligible change can occur in the amplitude of the bias current I O during one period of the squarewave modulating signal.
  • Flux modulation of amplitude 1/2 ⁇ O and frequency F/4 is applied to the SQUID loop or ring 10 by means of a modulation coil 52 from the binary counter 32 through a current limiting resistor 54". After any squarewave signal at frequency F is balanced in the manner described above, the resulting signal is applied to a signal demodulator 56.
  • An exclusive OR gate 58 and time delay circuit 60 are used to generate the proper reference signal from the F/4 output of the binary counter for the signal demodulator 56.
  • the exclusive OR gate 58 operates to mix the two frequencies F and F/4 in exactly the same manner that the two signals are mixed by the SQUID. This operation can be better understood by reference to the timing diagrams in FIG. 5.
  • the output from the signal demodulator 56 is then amplified by an amplifier 62.
  • the output of the amplifier can be used as an open loop output. In this case the output from the SQUID amplifier system will have a periodic character similar to the curve shown in FIG. 3. If a linear response is desired, the output of the amplifier may be applied to an integrator/filter circuit 64 and applied as a feedback signal through a resistor 66 to the feedback coil 52 by closing a switch 68. Thus a feedback loop is provided with the output being derived from the integrator/filter 64. It should be noted that, while a ratio of 4 : 1 between the switching frequency and the modulation frequency has been used, no particular ratio is required to make the circuit operate. This ratio was selected because it keeps the converted signal frequencies well separated from the bias switching frequency.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Magnetic Variables (AREA)
  • Superconductor Devices And Manufacturing Methods Thereof (AREA)

Abstract

A circuit for reducing low frequency noise in a direct current biased superconducting quantum interference device (10). A squarewave bias signal (IO) having no dc component is used to bias the two junctions (12, 14) of the dc SQUID (10). At the same time, the magnetic flux in the SQUID is modulated (32, 52) to heterodyne the input signals up to some convenient frequency where they may be amplified (44) without concern for drift. Final demodulation (48) automatically adjusts for the fact that the relative phase is reversed each time the squarewave bias (IO) changes polarity states.

Description

AC BIASING OF A DC SQUID Field of the Invention
This invention relates to measuring circuits using superconducting quantum interference devices (SQUID) , and more particularly, to a biasing arrangement for reducing low frequency noise.
Background of the Invention
Quantum interference effects in superconducting rings containing one or two Josephson junctions are well known. Devices exhibiting these effects, known as superconducting quantum interference devices or SQUIDS, have been used, for example, in the measurement of magnetic fields and voltages. Both dc SQUIDS using two Josephson junctions connected in a superconducting ring and RF SQUIDS incorporating a single junction in a superconducting ring have been used for making such measurements. Such dc SQUIDS have recently been constructed using thin film Josephson junctions having oxide or semiconductor barriers. Such dc SQUIDS have been shown to have advantages in regard to magnetic energy sensitivity compared to the RF SQUID. The construction and operation of tunnel junction dc SQUIDS is described in detail in the article "Tunnel Junction dc SQUID: Fabrication, Operation, and Performance" by Clarke, Goubau, and Ketchen, Journal of Low Temperature Physics, Vol. 25, Nos. 1/2, 1976, pp. 99-143. Recent efforts at obtaining improved energy sensitivity have involved the use of very small area junctions which, because of their relatively low capacitance, make possible higher resistance SQUIDS. Such small area junctions (approximately 1μ diameter) are able to operate in the earth's ambient field, thus avoiding the problem of providing a low field environment.
The principal problem with these small area junctions has been their tendency to exhibit a large amount of low frequency noise having a 1/f energy spectral density. This effect has been observed and analyzed as resulting from the thermodynamic temperature fluctuations in the superconducting material on either side of the junctions. The amplitude of these fluctuations is inversely proportional to the volume of material so that the smaller the junction, the greater the amplitude of these fluctuations. These fluctuations produce variations in the resistance of the junctions, and since a dc bias is normally impressed across the junctions, these resistance changes give rise to current fluctuations having the same 1/f spectral distribution as the original temperature fluctuations. Summary of the Invention The present invention is directed to a biasing arrangement for a dc SQUID which removes substantially all l/f (low frequency) noise from the output signal of the SQUID. Thus the circuit is able to take full advantage of the high frequency sensitivity of very small area thin film junctions. This is achieved, in brief, by providing a biasing circuit for a dc SQUID having a pair of thin film Josephson junctions connected in a superconducting ring wherein a bias current is caused to flow through the two junctions in parallel alternately in one direction and then in the opposite direction by a squarewave oscillator. This squarewave bias has no dc component. The operating characteristics of Josephson junctions are symmetric so the SQUIDS operate normally except during the relatively short transition time of the polarity reversal. The effect is to heterodyne the signal up to frequency bands centered around the squarewave frequency and its harmonics, which frequency is chosen to be well above any signal frequencies of interest, as well as the frequency at which the 1/f noise is significant.
Brief Description of the Drawings
For a more complete understanding of the invention reference should be made to the accompanying drawings, wherein: FIG. 1 is a schematic showing of a dc SQUID;
FIGS. 2 and 3 are graphical representations useful in explaining the operation of the present invention;
FIG. 4 is a schematic block diagram of the preferred embodiment of the present invention; and FIG. 5 is a timing diagram showing waveforms at various points in the circuit of FIG. 4.
Detailed Description
As described in detail in the above-identified publication and shown schematically in FIG. 1, the basic dc SQUID includes a low inductance superconducting loop 10 interrupted by two matched Josephson junctions 12 and 14. When a dc biasing current IB is passed through the two junctions in parallel, the voltage VJ varies as a function of the flux Φ A threading the ring. The voltage, in fact, is an oscillatory function of the flux in which one period corresponds to one flux quantum ΦO. FIG. 2 is graphical plot showing the change in the voltage VJ as a function of the biasing current IB . At a critical biasing current IB, the voltage varies between two limits, indicated at A and C. As the flux varies between an integral number of flux quanta n Φ O and an integral number plus a half quanta of flux (n + 1/2) Φ O. The oscillatory change of the voltage VJ with changes in flux at a given bias, current IB is shown in FIG. 3. Because of the symmetrical nature of the Josephson junctions, the same characteristic is observed at a bias current - IB of the same magnitude but of opposite polarity. The voltage across the junctions, of course, is reversed in polarity and has an average value - VO which varies between points B and D with changes in flux Φ threading the loop. As shown in FIG. 3, the voltage changes at the two operating points are opposite in phase.
Whereas in the past, it has been the practice to operate the dc SQUID at a substantially constant bias current level, the present invention utilizes a squarewave signal for generating the bias current IB so that the operating point is switched each half cycle of the squarewave between the levels +IB and -IB. The frequency F of the squarewave is selected above the normal range of signals being measured and preferably is in the order of 0.5 megahertz. By periodically reversing the bias current, differential noise current fluctuations which are generated in the junctions are caused to reverse their phase at frequency F. Because the phase of the voltage VJ as a function of flux is also reversed each time the bias current polarity changes, the net effect on the fluctuation noise due to the double phase reversal is that it is not mixed or heterodyned by the bias current switching. Actual signals in the form of flux changes linking the SQUID are heterodyned, however, and appear as side bands around the switching frequency F and its harmonics. Thus signal variations and noise fluctuations can be distinguished. in the past it has been the practice to incorporate the dc SQUID" in a feedback system. As described in the above publication, an ac magnetic field is applied to the SQUID by a feedback coil with a peak-to-peak amplitude of approximately 1/2 ΦO. The ac signal developed across the junctions is detected with a lock-in at the fundamental frequency. The same ac signal which modulates the SQUID is used to demodulate the output signal after it is amplified.
The preent invention superimposes the bias switching on the modulation and demodulation scheme used in the feedback loop. The preferred embodiment for implementing the invention is shown in detail in FIG. 4, which operates to both switch the bias and apply modulation to the SQUID and then demodulate the resulting mixture to recover the original input signal spectrum. The waveforms shown in FIG. 5 are useful in analyzing the operation of the circuit in the time domain.
Referring to FIG. 4 in detail, the SQUID, with its Josephson tunnel junctions 12 and 14 connected in a superconductive ring 10, is connected as one leg of a bridge circuit. A second adjacent leg of the bridge circuit is a resistor 16. The other two legs of the bridge circuit include respectively a resistor 18, capacitor 20 and bias modulator 22 forming one leg, and a resistor 24, capacitor 26 and balance modulator 28 forming the other leg. A squarewave voltage is applied across one diagonal of the bridge by a squarewave oscillator 30 running at a frequency 2F and binary counter 32 which generates output squarewaves at frequencies F and F/4.
The bias modulator 22 in combination with the resistor 18 and capacitor 20 controls the amplitude of the switched bias current driven in parallel through the Josephson junctions 12 and 14. The bias modulator 22 is controlled by a feedback circuit, described below. It automatically adjusts the amplitude of the switched current applied to the junctions, biasing them alternately between the average voltages +VO and -VO, as shown in FIG. 2. The actual information signal is in the small amplitude variations around +VO and -VO which are induced by flux changes in the loop 10, such as by an input signal applied to an input coil 34 associated with the SQUID. These voltage variations are detected by an output transformer 36 whose primary winding 38 is connected through a blocking capacitor 40 across the other diagonal of the bridge circuit. The secondary winding 42 of the transformer is connected to an RF amplifier 44. Thus the carrier voltage appears as a common mode signal at the transformer input and is rejected while any variations of the junction voltage from the nominal values -VO appear differentially at the transformer and are amplified by the RF amplifier 44. The actual value of VO is set by adjusting the amplitude control signal VB on the input of the balance modulator 28. The adjustable bias voltage source may be a potentiometer or similar device for controlling the output voltage of the balance modulator 28.
Any carrier signal at frequency F which has been amplified by the RF amplifier 44 is demodulated by a bias demodulator 48. The output of the bias demodulator 48 is an error signal which is integrated by an integrator circuit 50 and applied to the bias modulator 22 to control the output voltage level of the bias modulator. It should be noted that it would be possible to arrange this circuit to manually set the junction bias current and have the bias voltage automatically adjusted. However, because the voltage is less prone to variation than the operating current, adjustment of the voltage as the independent variable is preferred. The time constant of the integrator 50 is made long enough so that negligible change can occur in the amplitude of the bias current IO during one period of the squarewave modulating signal.
Flux modulation of amplitude 1/2 ΦO and frequency F/4 is applied to the SQUID loop or ring 10 by means of a modulation coil 52 from the binary counter 32 through a current limiting resistor 54". After any squarewave signal at frequency F is balanced in the manner described above, the resulting signal is applied to a signal demodulator 56. An exclusive OR gate 58 and time delay circuit 60 are used to generate the proper reference signal from the F/4 output of the binary counter for the signal demodulator 56. The exclusive OR gate 58 operates to mix the two frequencies F and F/4 in exactly the same manner that the two signals are mixed by the SQUID. This operation can be better understood by reference to the timing diagrams in FIG. 5. The output from the signal demodulator 56 is then amplified by an amplifier 62. The output of the amplifier can be used as an open loop output. In this case the output from the SQUID amplifier system will have a periodic character similar to the curve shown in FIG. 3. If a linear response is desired, the output of the amplifier may be applied to an integrator/filter circuit 64 and applied as a feedback signal through a resistor 66 to the feedback coil 52 by closing a switch 68. Thus a feedback loop is provided with the output being derived from the integrator/filter 64. It should be noted that, while a ratio of 4 : 1 between the switching frequency and the modulation frequency has been used, no particular ratio is required to make the circuit operate. This ratio was selected because it keeps the converted signal frequencies well separated from the bias switching frequency.

Claims

WHAT IS CLAIMED IS:
1. A control circuit for a dc SQUID having a pair of Josephson junctions connected in a superconductive loop, characterized by having means for applying a bias current through the pair of junctions in parallel, and means for reversing the polarity of the bias current periodically at a first predetermined frequency.
2. Apparatus of claim 1 further characterized by modulation means for producing a circulating current in the loop through the two junctions in series at a second predetermined frequency, and means for generating an output signal in response to the voltage across said two junctions in parallel.
3. Apparatus of claim 2 further characterized by means subtracting a voltage from said output signal corresponding to the voltage across said junctions from said bias current.
4. Apparatus of claim 3 further characterized by means responsive to the output from said subtracting means for demodulating the output to remove the second predetermined frequency from said output.
5. Apparatus of claim 4 wherein said subtracting means comprises a bridge circuit having the loop and pair of junctions in parallel connected as one arm of the bridge, and said means applying a bias current includes a squarewave source connected across one diagonal of the bridge.
6. Apparatus of claim 2 wherein said modulation means includes a carrier source of said second predetermined frequency, the carrier source being a squarewave source having a frequency that is integrally related to the frequency of the bias current.
7. Apparatus of claim 6 wherein the bias current frequency is four times the modulation carrier frequency.
PCT/US1981/000791 1980-06-17 1981-06-11 Ac biasing of a dc squid WO1981003710A1 (en)

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Application Number Priority Date Filing Date Title
DE8181901786T DE3176411D1 (en) 1980-06-17 1981-06-11 Ac biasing of a dc squid

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US06/160,225 US4389612A (en) 1980-06-17 1980-06-17 Apparatus for reducing low frequency noise in dc biased SQUIDS
US160225 1988-02-25

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EP (1) EP0053625B1 (en)
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CA (1) CA1195734A (en)
DE (1) DE3176411D1 (en)
WO (1) WO1981003710A1 (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0212452A2 (en) * 1985-08-20 1987-03-04 Siemens Aktiengesellschaft Measuring apparatus for a SQUID magnetometer
EP0289414A2 (en) * 1987-04-28 1988-11-02 Commissariat A L'energie Atomique Method and device for the digitization and linearization of a quasi-sinusoidal sensor
EP0433482A1 (en) * 1989-12-20 1991-06-26 Siemens Aktiengesellschaft Squid sensor apparatus with inductive coupling of an input signal into a squid
WO1991018298A1 (en) * 1990-05-15 1991-11-28 Valtion Teknillinen Tutkimuskeskus Method and apparatus for processing the output signal from a low-noise sensor
EP0461742A2 (en) * 1990-02-15 1991-12-18 Fujitsu Limited Digital magnetic flux measuring apparatus using superconducting quantum interference device
EP0474235A2 (en) * 1990-09-07 1992-03-11 Daikin Industries, Limited Magnetic flux locking method and apparatus
US5287058A (en) * 1990-02-15 1994-02-15 Fujitsu Limited Digital magnetic flux measuring apparatus using superconducting quantum interference device with flux trapping prevention features
CN102426343A (en) * 2011-08-31 2012-04-25 中国科学院上海微系统与信息技术研究所 Readout circuit based on SQUID (Superconducting Quantum Interference Device) offset voltage reversal and method for inhibiting low-frequency noises
EP2780732A4 (en) * 2011-11-14 2015-11-11 Neocera Llc Dc squid based rf magnetometer operating at a bandwidth of 200 mhz and higher
WO2022216377A1 (en) * 2021-04-07 2022-10-13 Microsoft Technology Licensing, Llc Superconducting output amplifier having return to zero to non-return to zero converters

Families Citing this family (72)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4588947A (en) * 1983-12-30 1986-05-13 International Business Machines Corporation Integrated miniature DC SQUID susceptometer for measuring properties of very small samples
US4585999A (en) * 1984-04-27 1986-04-29 The United States Of America As Represented By The United States Department Of Energy Radiofrequency amplifier based on a dc superconducting quantum interference device
DE3650062T2 (en) * 1985-06-07 1995-01-19 Hitachi Ltd Superconducting current sensor circuit.
US4663590A (en) * 1985-11-06 1987-05-05 Sperry Corporation Single frequency noise reduction circuit for squids
JPH0672913B2 (en) * 1986-12-18 1994-09-14 新技術事業団 Magnetic flux measurement device
US4906930A (en) * 1987-02-27 1990-03-06 Hitachi, Ltd. Magnetometer using a Josephson device and superconducting phototransistor
US4793355A (en) * 1987-04-17 1988-12-27 Biomagnetic Technologies, Inc. Apparatus for process for making biomagnetic measurements
FR2622020B1 (en) * 1987-10-20 1990-02-02 Thomson Csf SUPERCONDUCTING MAGNETOMETRIC DEVICE
US5020538A (en) * 1988-08-12 1991-06-04 Sam Technology, Inc. Low noise magnetoencephalogram system and method
US4947118A (en) * 1988-11-21 1990-08-07 Fujitsu Limited Digital squid system adaptive for integrated circuit construction and having high accuracy
EP0384928B1 (en) * 1989-03-01 1993-06-23 Siemens Aktiengesellschaft Circuitry for a squid gradiometer for the measurement of low intensity biomagnetic fields
US5254945A (en) * 1989-06-30 1993-10-19 Sharp Kabushiki Kaisha Magneto-resistive superconductive device and method for sensing magnetic fields
DE3926917A1 (en) * 1989-08-16 1991-02-21 Philips Patentverwaltung METHOD FOR SUPPRESSING CURRENT DISTRIBUTION NOISE IN A DC SQUID
US5189420A (en) * 1990-06-08 1993-02-23 The Mitre Corporation Method and apparatus for direct analog to formatted digital number conversion
US5053834A (en) * 1990-08-31 1991-10-01 Quantum Magnetics, Inc. High symmetry dc SQUID system
US5103682A (en) * 1990-11-05 1992-04-14 The United States Of America As Represented By The Secretary Of Commerce Ultra-sensitive force detector employing servo-stabilized tunneling junction
JP2662903B2 (en) * 1991-02-22 1997-10-15 セイコーインスツルメンツ株式会社 High sensitivity magnetic field detector
JPH04269680A (en) * 1991-02-25 1992-09-25 Seiko Instr Inc High sensitivity magnetic field detector
JP3133830B2 (en) * 1992-07-24 2001-02-13 富士通株式会社 SQUID magnetometer
DE4227876A1 (en) * 1992-08-22 1994-02-24 Philips Patentverwaltung Circuit arrangement for operating a SQUID, in particular a DC SQUID
US5387864A (en) * 1993-07-26 1995-02-07 The United States Of America As Represented By The Secretary Of The Navy Channel equalized DC squid flux-locked loop
ZA947132B (en) * 1993-09-15 1995-05-15 Commw Scient Ind Res Org Squid detector for tem prospecting
US5574369A (en) * 1994-08-19 1996-11-12 Hibbs; Andrew D. Detection and communications device employing stochastic resonance
JP3360550B2 (en) * 1996-10-17 2002-12-24 住友電気工業株式会社 Magnetic sensor drive circuit device
US6263189B1 (en) * 1997-09-29 2001-07-17 The Regents Of The University Of California Narrowband high temperature superconducting receiver for low frequency radio waves
US6420868B1 (en) 2000-06-16 2002-07-16 Honeywell International Inc. Read-out electronics for DC squid magnetic measurements
US6448767B1 (en) 2000-06-16 2002-09-10 Honeywell International, Inc. Fast flux locked loop
US6356078B1 (en) 2000-06-16 2002-03-12 Honeywell International Inc. Frequency multiplexed flux locked loop architecture providing an array of DC SQUIDS having both shared and unshared components
ITRM20040515A1 (en) * 2004-10-20 2005-01-20 Consiglio Nazionale Ricerche SUPERCONDUCTOR MAGNETOMETER DEVICE, AND ITS MEASUREMENT PROCEDURE.
GB0522968D0 (en) 2005-11-11 2005-12-21 Popovich Milan M Holographic illumination device
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US9335604B2 (en) 2013-12-11 2016-05-10 Milan Momcilo Popovich Holographic waveguide display
US11726332B2 (en) 2009-04-27 2023-08-15 Digilens Inc. Diffractive projection apparatus
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US10670876B2 (en) 2011-08-24 2020-06-02 Digilens Inc. Waveguide laser illuminator incorporating a despeckler
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WO2013167864A1 (en) 2012-05-11 2013-11-14 Milan Momcilo Popovich Apparatus for eye tracking
US9933684B2 (en) * 2012-11-16 2018-04-03 Rockwell Collins, Inc. Transparent waveguide display providing upper and lower fields of view having a specific light output aperture configuration
US10209517B2 (en) 2013-05-20 2019-02-19 Digilens, Inc. Holographic waveguide eye tracker
US9727772B2 (en) 2013-07-31 2017-08-08 Digilens, Inc. Method and apparatus for contact image sensing
CN105203978B (en) * 2014-06-03 2018-04-03 中国科学院上海微系统与信息技术研究所 A kind of losing lock of SQUID Magnetic Sensors resets compensation device and method
WO2016020632A1 (en) 2014-08-08 2016-02-11 Milan Momcilo Popovich Method for holographic mastering and replication
WO2016042283A1 (en) 2014-09-19 2016-03-24 Milan Momcilo Popovich Method and apparatus for generating input images for holographic waveguide displays
US10423222B2 (en) 2014-09-26 2019-09-24 Digilens Inc. Holographic waveguide optical tracker
EP3245551B1 (en) 2015-01-12 2019-09-18 DigiLens Inc. Waveguide light field displays
CN107873086B (en) 2015-01-12 2020-03-20 迪吉伦斯公司 Environmentally isolated waveguide display
JP6867947B2 (en) 2015-01-20 2021-05-12 ディジレンズ インコーポレイテッド Holographic waveguide rider
US9632226B2 (en) 2015-02-12 2017-04-25 Digilens Inc. Waveguide grating device
WO2016146963A1 (en) 2015-03-16 2016-09-22 Popovich, Milan, Momcilo Waveguide device incorporating a light pipe
WO2016156776A1 (en) 2015-03-31 2016-10-06 Milan Momcilo Popovich Method and apparatus for contact image sensing
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EP3433658B1 (en) 2016-04-11 2023-08-09 DigiLens, Inc. Holographic waveguide apparatus for structured light projection
EP3548939A4 (en) 2016-12-02 2020-11-25 DigiLens Inc. Waveguide device with uniform output illumination
US10545346B2 (en) 2017-01-05 2020-01-28 Digilens Inc. Wearable heads up displays
EP3698214A4 (en) 2017-10-16 2021-10-27 Digilens Inc. Systems and methods for multiplying the image resolution of a pixelated display
JP7404243B2 (en) 2018-01-08 2023-12-25 ディジレンズ インコーポレイテッド Systems and methods for high-throughput recording of holographic gratings in waveguide cells
WO2019136476A1 (en) 2018-01-08 2019-07-11 Digilens, Inc. Waveguide architectures and related methods of manufacturing
KR20200104402A (en) 2018-01-08 2020-09-03 디지렌즈 인코포레이티드. Systems and methods for manufacturing waveguide cells
EP4372451A3 (en) 2018-03-16 2024-08-14 Digilens Inc. Holographic waveguides incorporating birefringence control and methods for their fabrication
US11402801B2 (en) 2018-07-25 2022-08-02 Digilens Inc. Systems and methods for fabricating a multilayer optical structure
EP3924759A4 (en) 2019-02-15 2022-12-28 Digilens Inc. Methods and apparatuses for providing a holographic waveguide display using integrated gratings
US10802086B2 (en) 2019-03-06 2020-10-13 United States Of America As Represented By The Secretary Of The Navy Circuits and method for biasing magnetic flux through a superconducting quantum interference array
JP2022525165A (en) 2019-03-12 2022-05-11 ディジレンズ インコーポレイテッド Holographic Waveguide Backlights and Related Manufacturing Methods
WO2020247930A1 (en) 2019-06-07 2020-12-10 Digilens Inc. Waveguides incorporating transmissive and reflective gratings and related methods of manufacturing
US11681143B2 (en) 2019-07-29 2023-06-20 Digilens Inc. Methods and apparatus for multiplying the image resolution and field-of-view of a pixelated display
EP4022370A4 (en) 2019-08-29 2023-08-30 Digilens Inc. Evacuating bragg gratings and methods of manufacturing
US11630166B1 (en) 2021-08-30 2023-04-18 United States Of America As Represented By The Secretary Of The Navy Superconducting quantum interference array receiver and method for digitally controlling magnetic flux bias thereof

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3528005A (en) * 1967-11-16 1970-09-08 Trw Inc Ultra-sensitive magnetic gradiometer using weakly coupled superconductors connected in the manner of a figure eight

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
A. ROSEN et al "Magnetic Recordings of the Heart's Electrical Activity with a Cryogenic Magnetometer" Vol. 42 No. 10, published September 1971 by Journal of Applied Physics pp 3682-3684. *
J. CLARKE "Advances in SQUID Magnetometers" Vol. E-27, No. 10, published October 1980 by IEE Transactions on Electron Devices pp 1896-1908. *
J. CLARKE et al "A Reliable DC SQUID Made with Tunnel Junctions" Vol. MAG-11 No. 2, published March 1975 by IEE Transactions on Magnetics pp 724-727. *

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0212452A2 (en) * 1985-08-20 1987-03-04 Siemens Aktiengesellschaft Measuring apparatus for a SQUID magnetometer
EP0212452A3 (en) * 1985-08-20 1987-07-15 Siemens Aktiengesellschaft Berlin Und Munchen Measuring apparatus for a squid magnetometer
EP0289414A2 (en) * 1987-04-28 1988-11-02 Commissariat A L'energie Atomique Method and device for the digitization and linearization of a quasi-sinusoidal sensor
FR2614695A1 (en) * 1987-04-28 1988-11-04 Commissariat Energie Atomique METHOD FOR SCANNING AND LINEARIZING A QUASI SINUSOIDAL PERIODIC CHARACTERISTIC SENSOR AND CORRESPONDING DEVICE
EP0289414A3 (en) * 1987-04-28 1988-11-09 Commissariat A L'energie Atomique Method and device for the digitization and linearization of a quasi-sinusoidal sensor
US4933888A (en) * 1987-04-28 1990-06-12 Commissariat A L'energie Atomique Process for the digitization and linearization of a transducer with a quasi-sinusoidal periodic characteristic and corresponding apparatus
EP0433482A1 (en) * 1989-12-20 1991-06-26 Siemens Aktiengesellschaft Squid sensor apparatus with inductive coupling of an input signal into a squid
EP0461742A2 (en) * 1990-02-15 1991-12-18 Fujitsu Limited Digital magnetic flux measuring apparatus using superconducting quantum interference device
EP0461742A3 (en) * 1990-02-15 1992-11-19 Fujitsu Limited Digital magnetic flux measuring apparatus using superconducting quantum interference device
US5287058A (en) * 1990-02-15 1994-02-15 Fujitsu Limited Digital magnetic flux measuring apparatus using superconducting quantum interference device with flux trapping prevention features
WO1991018298A1 (en) * 1990-05-15 1991-11-28 Valtion Teknillinen Tutkimuskeskus Method and apparatus for processing the output signal from a low-noise sensor
US5488295A (en) * 1990-05-15 1996-01-30 Valtion Teknillinen Tutkimuskeskus Method and apparatus for cancelling noise of a low-noise sensor
EP0474235A2 (en) * 1990-09-07 1992-03-11 Daikin Industries, Limited Magnetic flux locking method and apparatus
EP0474235A3 (en) * 1990-09-07 1993-04-07 Daikin Industries, Limited Magnetic flux locking method and apparatus
CN102426343A (en) * 2011-08-31 2012-04-25 中国科学院上海微系统与信息技术研究所 Readout circuit based on SQUID (Superconducting Quantum Interference Device) offset voltage reversal and method for inhibiting low-frequency noises
CN102426343B (en) * 2011-08-31 2014-03-26 中国科学院上海微系统与信息技术研究所 Readout circuit based on SQUID (Superconducting Quantum Interference Device) offset voltage reversal and method for inhibiting low-frequency noises
EP2780732A4 (en) * 2011-11-14 2015-11-11 Neocera Llc Dc squid based rf magnetometer operating at a bandwidth of 200 mhz and higher
WO2022216377A1 (en) * 2021-04-07 2022-10-13 Microsoft Technology Licensing, Llc Superconducting output amplifier having return to zero to non-return to zero converters
US11668769B2 (en) 2021-04-07 2023-06-06 Microsoft Technology Licensing, Llc Superconducting output amplifier having return to zero to non-return to zero converters

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EP0053625B1 (en) 1987-09-02
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EP0053625A4 (en) 1982-10-07
US4389612A (en) 1983-06-21
CA1195734A (en) 1985-10-22

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